USE OF A SMALL-BORE INTERNAL-SURFACE REVERSED-PHASE SILICA COLUMN FOR THE MICRO HIGH-PERFORMANCE FRONTAL ANALYSIS OF CARBAMAZEPINE IN AN ALBUMIN SOLUTION WITH A SMALL SAMPLE VOLUME

A micro high-performance frontal analysis (MHPFA) using a small-bore internal-surface reversed-phase silica column (10 cmX1.0 mm or 1.5 mm i.d.) was developed for the simultaneous determination of the total and unbound carbamazepine (CBZ) concentrations in a human serum albumin (HSA) solution. When a 100-mul or 200-mul portion of a 4-12 mug/ml CBZ solution containing 593 muM HSA was directly injected into the column, CBZ gave a trapezoidal peak with the plateau being separated from the HSA peak. The CBZ concentration, calculated from the plateau height, agreed well with the unbound drug concentration determined by the conventional ultrafiltration-HPLC method, and the CBZ concentration calculated from the peak area coincided with the total concentration. The reproducibility was satisfactory (RSD, <3.79%, n=5 or 6). The use of a glass-lined stainless-steel column and an injector-reswitching technique, which prevents the introduction of a diffused portion of the sample solution into the column, was necessary for a frontal analysis using these small-bore columns. The present MHPFA reduced the sample volume to as low as one-seventh of that required for HPFA using an internal-surface reversed-phase silica column of conventional size (15 cmX4.6 mm i.d.).